Sitting at a desk for eight hours a day really adds up. What's worse is that research shows that regular, inactive sitting is the "new smoking" and may increase your risk of heart disease, cancer, diabetes—even if you do exercise regularly, according to Runner's World.

In order to boost circulation, challenge your core, and practice good posture all day long, consider taking advantage of active sitting. This lifestyle upgrade doesn't even require you to break a sweat to be healthier. Here are three ways to sit fit at the office.

Upgrade Your Office Chair

According to The Huffington Post, dynamic chairs and balance balls, which put you on a less stable surface and require you to actively engage your muscles throughout the day, work to reverse the negative effects of sitting for too long. First, they have you sitting at a higher level than a typical office chair, and that increased hip angle demands more work from your core and allows your spine to sit in a more natural position. The unstable surface also engages more stabilizer muscles—just like when you use unstable surfaces while exercising. Check out dynamic chairs that are currently on the market for a comfy but challenging respite while you work.

Try Standing at Your Desk

Why not ditch your chair altogether? According to The Boston Globe, research shows an increase in mood and energy levels from those who stood during part of their work day. And although standing all day isn't necessarily the answer for burning calories, it is a gateway to more activity throughout the day, and will likely lead to getting up to talk with a colleague rather than just calling or e-mailing them.

Schedule Walking Intervals

The best way to practice active sitting is to take your workload on the move. Schedule in a short walking session every hour, or a longer walk a few times a day. After all, the 10,000-steps-per-day rule is hard to meet if you drive to work and don't exercise every day. So whether you're clearing your head or working on the go, short walks throughout the day can help you get in your daily steps. You may even find that you're more productive when you return to sitting at your desk.

Both your body and mind can reap the benefits of active sitting. Start with these three ideas and use your creativity to come up with ways to stay on the move during the workday.